Palaeoenvironmental significance of charophyte gyrogonites from Laguna de Gallocanta (Aragón, Spain)

Abstract

At a distance of about 170 km from the Mediterranean, the inland salt lake Laguna de Gallocanta (995 m a.s.l.) is an important stop-over for thousands of migratory water birds and represents an athallasic occurrence of Lamprothamnium papulosum (Wallr.) J. Groves and Chara galioides DC., which were recorded growing in the lake until 1990. These two charophyte species are typically also known from Mediterranean coastal brackish water sites. The material studied here consists of (i) gyrogonites collected from surface sediments in Laguna de Gallocanta and (ii) fossil gyrogonites recovered from the upper 35 cm of a 75 cm core obtained from the lake. Detailed morphological and biometrical analysis of L. papulosum is provided and compared with previous data from South France. The size and shape of the gyrogonites from Laguna de Gallocanta differ greatly from populations growing in coastal sites. These differences are considered to be an adaptive morphological response to the particular hydro-chemical conditions prevailing in Laguna de Gallocanta whose salinity is due to the outwash of sulphate-rich waters from the underground. The distribution and frequency changes of the charophyte species along the core profile allow inferring palaeoecological changes marked by lake-level lowering and increasing salinity.